1. Field of the Invention
The present invention relates to detergent compositions for use in washing delicate fabrics such as woolen and silk, and more particularly, to liquid detergent compositions for such use which are free of inorganic builder salts, have a mild pH value, and may be employed as handwashing or machine washing detergents.
2. Description of Related Art
Detergents which are considered to be suitable for washing extremely delicate fabrics of wool or silk are known. In general, they produce a neutral to mildly alkaline reaction and, in addition to synthetic anionic surfactants, such as alkylbenzene sulfonate, fatty alcohol sulfate or alkylglycolether sulfate, often contain nonionic or cationic compounds. The nonionic surfactants are for the purpose of increasing detergency, while the cationic compounds are present to improve the softness and feel of the washed fabrics. Unfortunately, it has been found that detergents containing only alkylbenzene sulfonate as the synthetic anionic surfactant can damage the fiber structure of delicate, washable wools, particularly merino and angora wool, in the event of repeated use, whereas fatty alcohol sulfates, for example, show inadequate detergency at the necessary low washing temperatures. In cases such as these, nonionic surfactants have proven equally unfavorable because woolen fabrics washed with them feel comparatively hard and brittle. These effects may be much more serious in the case of machine washing. The addition of softening cationic surfactants, as recommended for such purposes, does not fully compensate for the loss of feel and, where anionic surfactants are present at the same time, leads to a reduction in detergency.
The addition of builder salts, such as mildly alkaline pyrophosphates or free alkanolamine, has also been recommended to increase detergency, but unfortunately their use also leads to a loss of quality in the case of particularly delicate woolen fabrics and knitwear. Fatty acid mono and diethanolamides are also known additives for light-duty detergents. However, because of their high foaming power, the washing liquid frequently overfoams in machine washing, particularly when using automatic washing machines having a horizontally mounted drum. This applies in particular where foam-active anionic surfactants are present.
Another requirement which high-quality wool detergents have to satisfy is that they should not promote any bleeding of the fabric dyes. Only those wool detergents which satisfy certain minimum requirements with respect to 12 selected fabric dye finishes are considered as safe and allowed to bear the wool seal of the IWS (International Wool Secretariat, London and Duesseldorf). Accordingly, there is a need to provide a detergent which satisfies these more stringent requirements, and overcomes the aforenoted disadvantages.